Conventional window-type door assemblies for refrigeration units of the type used in supermarkets and the like comprise a frame having a thermo-pane mounted therein. The frame is composed of extruded aluminum frame members secured together by corner brackets. The thermo-pane normally comprises a pair of glass plates suitably spaced apart by spacer members disposed about the peripheries of the plates. An elastomeric gasket is secured between the frame and the edges of the plates in a conventional manner.
Standard door assemblies of this type are expensive to fabricate and assemble due to the large number of component parts involved and the labor intensive steps required for the assembly process. Further, a relatively high thermal conductivity is exhibited by the aluminum frame that induces undue conduction of heat within the refrigeration unit. In addition, an electrical heating system is normally required to prevent condensation on the glass plates composing the thermo-pane. The door assemblies also normally require the consumer-customer to close them manually, after it they have been opened for product procuring purposes.